Master of Science (MS)


Renewable Natural Resources

Document Type



Bioelectrical impedance analysis (BIA) has been proposed as an easy and accurate technique for a non-lethal index of condition in fish; however, factors affecting its accuracy have yet to be properly identified. The technique uses the resistance (R) and reactance (Xc) of water and lipids in contiguous tissues to estimate lipid content. Studies have investigated the use of BIA on fish, but with mixed results, possibly caused by unrecognized sources of influences. Our study explored possible sources of variance for BIA measurements in gulf killifish, Fundulus grandis, through laboratory feeding and fasting experiments, and experimental exposures to acute changes in temperature and salinity. In our feeding and fasting experiments, wild caught F. grandis were held in recirculating tanks and either fed ad libitum or withheld food for 28 days and sampled every 7 days. In the fed and fasted experiments, BIA measurements, plasma osmolarity, Lecren’s Kn, and % organ lipid were significantly different by day with most variables showing a gradual change over time (ANOVA, p <.05). However, in the fasted experiment BIA measurements did not follow the trends of declining condition indicated by Kn and % organ lipid In our experiments with environmental factors, fish acclimated to 24⁰C and 12 ppt salinity where exposed to tanks randomly assigned treatments of salinities 2, 12, 24 and temperatures 2, 12, 24⁰C. Reactance was consistently significantly higher at salinity 2 ppt, and R significantly decreased as temperature increased (ANOVA,Tukey-Kramer p <.05). Our results indicate additional possible sources of variance including sex, size, temperature and changes in body chemistry. Some of the mixed results from other studies may be explained by these sources of variance. If these sources of variance are shown to be easily correctable, BIA may prove to be an effective index of condition.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Green, Chris